1. Field of the Invention
The present invention pertains to a respiratory patient interface used to deliver gas to a user and a method for using the same. In particular, the present invention is related to a flexible, cheek mounted patient interface that includes self-adjustment features to enhance the patient's comfort.
2. Description of the Related Art
A variety of delivery systems are known that provide gas at positive pressure for consumption by the patient. The uses and applications of such systems vary. Some such systems have been developed for the treatment of sleep apnea and other sleep related disorders.
Sleep apnea syndrome results in episodic upper airway obstruction during sleep. As a consequence, there is repeated interruption of sleep in the patient. Positive airway pressure (PAP) devices have been developed to treat this disorder. A typical PAP device comprises a flow generator (e.g., a blower) that delivers gas via a delivery conduit to a patient interface, such as a mask. It is also known to deliver the PAP pressure as a continuous positive airway pressure (CPAP), a variable airway pressure, such as a bi-level pressure that varies with the patient's respiratory cycle, or an auto-titrating pressure that varies with the monitored condition of the patient. Pressure support therapies are also provided to treat other medical and respiratory disorders, such as Cheynes-Stokes respiration, congestive heart failure, and stroke.
Mask development has generally involved balancing of two competing goals: secure attachment to create an airtight seal in order to facilitate the required positive airway pressure, and comfort to the user in order to maximize patient compliance. An airtight seal can be achieved by tightening the mask down firmly against the patient's face. However, this solution oftentimes results in discomfort to the user due to relatively high strapping forces needed to ensure a secure seal against the patient and less than satisfactory patient compliance. Alternatively, the mask may be fit loosely on the patient's face to enhance comfort. However, the effectiveness of the mask may be compromised if it is too loose.
A variety of masks have been suggested in the art seeking to address one or both of the above noted issues. In order to enhance comfort and provide an adequate seal, several low contact masks have been suggested which minimize the contact area between the patient and the mask. For instance, U.S. Pat. No. 6,615,830 (“the '830 patent”) discloses a mask that includes a rigid shell having an aperture and a seal member connected to the shell and adapted to sealingly engage the region about the patient's nose. The seal has an internal cavity in fluid communication with the aperture of the rigid shell. The aperture of the rigid shell, in turn, is connected via a coupling to the distal end of a gas delivery conduit. In order to deliver gas to the patient, the proximal end of the conduit is connected to the positive airway pressure device, i.e., a flow generator. In order to secure the mask to the user, three radially extending ears are spaced about the rigid shell. Each ear provides at least one eyelet sized to receive a strap that encircles the patient's head to secure the nasal mask in place.
Although masks manufactured in accordance with the teachings of the '830 patent have performed well in the industry, such masks can still be further improved upon. To provide an adequate seal with the patient's face, the headgear assembly must be firmly tightened to pull the mask down about the patient's nose region. As the mask is tightened, the force exerted by the headgear is concentrated about the patient's nose and may be deemed uncomfortable by some patients. Moreover, this mask does not provide easy adjustability. The location of contact between the sealing member and the patient is fixed as a result of using a rigid collar and an immovable seal.
In order to further advance the art, other mask assemblies have been suggested that utilize separate regions of contact on the patient's face to distribute the force exerted by the headgear between the patient's forehead and nasal region. For instance, one such mask is described in published U.S. Patent Appln. No. US-2004-0045551-A1 (“the '551 application”). Similar to the previously described mask, the mask taught by the '551 application has a rigid shell with an aperture that engages an end of the coupling. A seal member, also referred to as a cushion, is attached to the shell and engages the region about the patient's nose. Extending from the shell is a pair of ears configured to be secured to the headgear via eyelets.
One distinguishing feature of this mask as compared to the mask disclosed in the '830 patent is that it includes a forehead stabilizer that contacts the patient's forehead. The stabilizer includes an arm that extends radially outwardly from the nasal portion of the mask. A pad support is pivotably attached to the end portion of a mechanically adjustable arm so that the pad can be properly located on the forehead of the patient. The pad support has an inner surface to which a pad is removably attached. The pad is manufactured from a flexible material that is capable of conforming to the contours of the patient's head thus enhancing comfort.
This mask provides several advantages over the prior art. For instance, it disperses the load over multiple locations on the user, i.e., the nasal region and the forehead region. By engaging the patient's face in multiple locations, the force exerted by the headgear is dispersed about the patient's face, thus enhancing the comfort associated with using this device. In addition, having multiple regions of contact with the patient's face is more secure than when the mask only engages one region of the user's face.
Although such devices have substantially advanced the art, addition improvements are still possible. For instance, the rigid construction of the shell, ears, and arm of this mask prevents it from being easily adjusted to fit different patients. The patient, or a caregiver, must manipulate various mechanical features in order to adjust this mask or multiple different sizes need to be constructed. Secondly, although having two separate engagement locations provides superior securement of the device compared with single point engagement, even this mask may move around on the patient's face unless the headgear is firmly tightened thus potentially resulting in discomfort to some patients. In order to properly fit, this nasal mask requires some manipulation by the patient or a caregiver.
Additional masks have been suggested to address the competing goals of comfort and stability. One such nasal mask, which is described in U.S. Pat. No. 6,019,101 (“the '101 patent”) has a flexible shell defined by a contoured portion circumscribing the nasal region of the patient with a pair of integral side wings designed to extend laterally over the patient's cheeks. A large gel-filled seal is disposed on the interior of the shell to provide a large airtight contact area with the patient's face. Even though this mask operates effectively for its intended purpose, it also has several disadvantages. This mask utilizes a large heavy seal attached to the rear surface of the shell in order to both seal and disperse compression forces about the nasal region of the user. In order to achieve both of these functions adequately, a large thick seal is required. Secondly, the seal is fixed to the shell thus preventing the seal from being adjusted to accommodate different users. Further, the seal abuts the face of the user about the nasal region thus concentrating a majority of the force exerted by the headgear in this region similar to the situation presented by the mask described in the '830 patent.
In light of the above, it is apparent that further advancements in the mask art would be desirable. For instance, it would be desirable to have a mask that provides stable and secure engagement about the patient's nasal region in order to maintain fluid communication with the PAP device. It would also be desirable to have a device that is configured to enhance the comfort experienced by the patient. In addition, it would also be desirable to have a nasal mask which can self-adjust so that a single device can adapt to a variety of different facial contours without manipulation by the user or caregiver. It would be further desirable to have a device that is configured to reduce the number of complex mechanical parts to reduce wear. Still further, it would be desirable to have a mask that avoids providing any structural features near the patient's eyes. This is particularly important for patient's who desire to where glasses while wearing the mask and for patient's that tend to feel claustrophobic when a structure is provided at or near their eyes. Avoiding the ocular area also eliminates or avoids the leakage of gas into the user's eyes, which can cause great discomfort. Finally, it would be desirable to have a mask that accomplishes these functions while also providing a relatively high degree of adjustability, so that a common mask style or configuration can be fitted to a variety of patients with deferent facial characteristics.